#30158: Subquery expressions unnecessarily added to group by
-------------------------------------+-------------------------------------
Reporter: Jonny Fuller | Owner: Simon
Type: | Charette
Cleanup/optimization | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: subquery, group_by | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 1 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Simon Charette):
I renamed the ticket because I'm pretty confident that the generated query
doesn't cause the wrong results to be returned.
The fact that the ORM doesn't have the introspection abilities to
determine if some annotated expressions can be trimmed from the `GROUP BY`
clause on aggregation
[https://github.com/django/django/blob/5c17c273ae2d7274f1fa78218b3b74690efddb86/django/db/models/sql/query.py#L407-L409
is a known limitation] and there's probably other existing issues for
other type of expressions.
Since the initial approach of making `get_group_by_cols` return an empty
list is not viable for the aforementioned reason I think we should begin
by merging [https://github.com/django/django/pull/11030 regression tests
to prevent this edge case from being overlooked in the future].
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Ticket URL: <https://code.djangoproject.com/ticket/30158#comment:13>
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